Dyeing composition for dyeing keratinous fibers comprising at least one particular dicationic diazo dye

ABSTRACT

The invention concerns a novel dyeing composition for dyeing keratinous fibers, in particular human hair, comprising a dicationic diazo dye of formula (I): W1—W2—N═N—W3—L—W4—N═N—W5—W6, as well as the dyeing method using said composition and the novel compounds of formula (I).

A subject matter of the invention is a novel dyeing composition for the dyeing of keratinous fibers, in particular of human hair, comprising a specific dicationic diazo dye and the process for dyeing keratinous fibers employing such a composition. Another subject matter of the invention is novel dicationic diazo dyes.

It is known to dye keratinous fibers and in particular human hair with dyeing compositions comprising oxidation dye precursors, generally known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidation bases are colorless or weakly colored compounds which, in combination with oxidizing substances, give rise to colored compounds by an oxidative coupling process.

It is also known that the hues obtained with these oxidation bases can be varied by combining them with couplers or coloring modifiers, the latter being chosen in particular from aromatic meta-diamines, meta-aminophenols meta-diphenols and certain heterocyclic compounds, such as indole compounds.

The variety of the molecules employed as oxidation bases and couplers makes it possible to obtain a rich palette of colors.

This oxidation dyeing process consists in applying, to the keratinous fibers, oxidation bases or a mixture of oxidation bases and of couplers with an oxidizing agent, for example aqueous hydrogen peroxide solution, in leaving to stand and in then rinsing the fibers. The colorations which result therefrom are permanent and powerful, and withstand external agents, in particular light, bad weather, washing, perspiration and rubbing. Generally applied at basic pH, they make it possible to obtain dyeing and simultaneously lightening of the fiber, which is reflected in practice by the possibility of obtaining a final coloration which is lighter than the original color. In addition, lightening the fiber has the advantageous effect of producing a unified color in the case of gray hair and, in the case of naturally pigmented hair, of making the color emerge, that is to say of rendering it more visible.

It is also known to dye human keratinous fibers by direct dyeing. The process conventionally used in direct dyeing consists in applying, to the keratinous fibers, direct dyes, which are colored and coloring molecules having an affinity for the fibers, in leaving to stand and in then rinsing the fibers.

It is known, for example, to use nitrobenzene, anthraquinone or nitropyridine direct dyes, azo, xanthene, acridine or azine dyes or triarylmethane dyes.

The colorations which result therefrom are particularly chromatic colorations which, however, are temporary or semipermanent because the nature of the interactions which bind the direct dyes to the keratinous fiber and their desorption from the surface and/or from the core of the fiber are responsible for their low dyeing power and for their poor resistance to washing or to perspiration. In addition, these direct dyes are generally sensitive to light, because of the low resistance of the chromophore with regard to photochemical attacks, and result over time in fading of the coloring of the hair. In addition, their sensitivity to light is dependent on their distribution, uniform or nonuniform, in the keratinous fiber.

It is known to use direct dyes in combination with oxidizing agents. However, direct dyes are generally sensitive to the action of oxidizing agents, such as aqueous hydrogen peroxide solution, and reducing agents, such as sodium bisulfite, which generally renders them difficult to use in compositions for lightening direct dyeing based on aqueous hydrogen peroxide solution and based on a basifying agent or in oxidation dyeing compositions in combination with oxidation dye precursors or couplers.

For example, provision has been made, in Patent Applications FR-1 584 965 and JP-062 711 435, to dye the hair with dyeing compositions based on direct nitro dyes and/or on disperse azo dyes and on aqueous ammoniacal hydrogen peroxide solution by applying, to the hair, a mixture of said dyes and of said oxidizing agent prepared immediately before use. However, the colorations obtained prove to be insufficiently persistent and disappear on shampooing, allowing the lightening of the hair fiber to become apparent. Such a coloration becomes unattractive on changing over time.

Provision has also been made, in Patent Applications JP-53 95693 and JP 55 022638, to dye the hair with compositions based on cationic direct dyes of oxazine type and on aqueous ammoniacal hydrogen peroxide solution by applying, to the hair, in a first stage, aqueous ammoniacal hydrogen peroxide solution and then, in a second stage, a composition based on the direct oxazine dye. This coloration is not satisfactory because of the fact that it requires a process rendered excessively slow by the leave-in times of the two successive stages. Furthermore, if a mixture prepared at the time of use of the direct oxazine dye with aqueous ammoniacal hydrogen peroxide solution is applied to the hair, no coloration is produced or, at least, a coloration of the hair fiber is obtained which is virtually nonexistent.

More recently, Patent Application FR 2 741 798 has disclosed dyeing compositions comprising direct azo or azomethine dyes comprising at least one quaternized nitrogen atom, said compositions having to be mixed at the time of use at basic pH with an oxidizing composition. These compositions make it possible to obtain colorations with homogeneous, persistent and bright highlights. However, they do not make it possible to dye keratinous fibers with as much power as with oxidation dyeing compositions.

There thus exists a real need to try to find chromatic direct dyes which make it possible to dye keratinous fibers as powerfully as oxidation dyes, which are as stable as them toward light and are also resistant to bad weather, washing and perspiration, and which, in addition, are sufficiently stable in the presence of oxidizing and reducing agents to be able to simultaneously obtain lightening of the fiber, either by use of lightening direct compositions comprising them or by the use of oxidation dyeing compositions comprising them. There also exists a real need to try to find direct dyes which make it possible to dye keratinous fibers in order to obtain a very broad range of colors, in particular highly chromatic colors, without forgetting the “basic” shades, such as the blacks and the browns.

These aims are achieved with the present invention, a subject matter of which is a composition for dyeing keratinous fibers, and in particular human keratinous fibers such as the hair, comprising at least one dicationic diazo dye of the following formula (I): W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆  Formula (I) in which

-   -   W₁ and W₆ represent, independently of one another, a radical         NR₁R₂     -   W₂ and W₅ represent, independently of one another, a         carbonaceous aromatic, pyridine or pyridazinyl group of formula         (II)     -   W₃ and W₄ represent, independently of one another, a         heteroaromatic radical represented by the following         formulae (III) and (IV):         in which     -   X₁ represents a nitrogen atom or a radical CR₅,     -   X₂ represents a nitrogen atom or a radical CR₆,     -   Z₁ represents an oxygen or sulfur atom or a radical NR₈,     -   Z₂ represents a nitrogen atom or a radical CR₉,     -   Z₃ represents a nitrogen atom or a radical CR₁₂,     -   Z₄ represents a nitrogen atom or a radical CR₁₃,     -   N¹ of the 5-membered ring of formula (III) is connected to the         group L and the bond a of the same 5-membered ring is connected         to the azo group of formula (I),     -   the bond b of the 6-membered ring of formula (IV) is connected         to the azo group of formula (I) and N¹ of the 6-membered ring of         formula (IV) is connected to the group L,     -   L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃         represent, together or independently of one another, a linear or         branched C₁-C₁₆ hydrocarbonaceous chain, which can form one or         more 3- to 6-membered carbonaceous rings, and which can be         saturated or unsaturated, of which one or more carbon atoms of         the carbonaceous chain can be replaced by an oxygen, nitrogen or         sulfur atom or by an SO₂ group, and the carbon atoms of which         can be, independently of one another, substituted by one or more         halogen atoms; R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and         R₁₃ can represent hydrogen; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉,         R₁₀, R₁₁, R₁₂ and R₁₃ not comprising a peroxide bond, or diazo         or nitroso radicals, and L is a divalent radical,     -   R₈ represents a linear or branched C₁-C₈ alkyl radical         optionally substituted by one or more radicals chosen from         hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂         (di)alkylamino, carboxyl or sulfonic radicals; an optionally         substituted phenyl radical,     -   R₇ with R₉, R₁₀ with R₁₁ and R₁₂ with R₁₃ can form a         carbonaceous aromatic ring such as a phenyl,     -   R is a C₁-C₃ alkyl radical,     -   X is an organic or inorganic anion.

In the context of the present invention, the term “alkyl”, unless otherwise stated, is understood to mean an alkyl radical comprising from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, which may be linear or branched. The term alkoxy means alkyl-O—, the term alkyl having the above meaning.

According to the invention, when it is indicated that one or more of the carbon atoms of the hydrocarbonaceous chain defined for the radicals L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can be replaced by an oxygen, nitrogen or sulfur atom or by an SO₂ group, and/or that these hydrocarbonaceous chains are unsaturated, this means that it is possible, by way of example, to carry out the following conversions:

can become

can become

can become

can become

can become

In particular, the expression “branched hydrocarbonaceous chain” is understood to mean a chain which can form one or more 3- to 6-membered carbonaceous rings. The expression unsaturated hydrocarbonaceous chain is understood to mean a chain which can comprise one or more double bonds and/or one or more triple bonds, it being possible for this hydrocarbonaceous chain to lead to aromatic groups.

X is an organic or inorganic anion, for example, chosen from a halide such as chloride, bromide, fluoride, iodide; a hydroxide; a sulfate; a hydrogen sulfate; a (C₁-C₆)alkyl sulfate such as for example a methyl sulfate or an ethyl sulfate; an acetate; a tartrate; an oxalate; a (C₁-C₆)alkyl sulfonate such as methyl sulfonate; an aryl sulfonate which is unsubstituted or substituted by a C₁-C₄ alkyl radical such as for example a 4-toluoyl sulfonate.

R₁ and R₂ represent, preferably and independently of one another, a hydrogen atom; a linear or branched C₁-C₆ alkyl radical, optionally substituted by one or more radicals chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals; a phenyl radical optionally substituted by one or more radicals chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals or a halogen atom such as chlorine, fluorine or bromine; a C₁-C₄ alkylsulfonyl radical; an arylsulfonyl radical; a radical chosen from pyrazolyl, imidazolyl, thiazolyl, oxazolyl, thiadiazolyl, triazolyl, pyrrolyl, pyridyl, pyrimidinyl, triazinyl, pyrazinyl and pyridazinyl radicals.

R₁ and R₂ together can form a 5-, 6-, 7- or 8-membered heterocyclic radical optionally substituted by one or more hydroxyl or amino radicals; a group —NR₁₄R₁₅ in which R₁₄ and R₁₅ represent, independently of one another, a hydrogen atom, a linear or branched C₁-C₄ alkyl radical substituted by one or more radicals chosen from a halogen atom, a hydroxyl, C₁-C₂ alkoxy, amino or C₁-C₂ amino(di)alkyl, or (poly)hydroxyalkylamino radical; a sulfonylamino radical; a carboxyl radical; a carboxamido radical; a C₁-C₆ alkyl radical optionally substituted by one or more hydroxyl or amino radicals; a group —NR₁₄R₁₅.

The asymmetric carbons of said 5-, 6-, 7- or 8-membered heterocycles may be of the (R) and/or (S) configuration.

R₁ and R₂ together can also form a 5- or 6-membered heteroaromatic radical such as pyrazole, imidazole, pyrrole, triazole, pyridazine, pyrimidine.

R₁ and R₂ represent, preferably and independently of one another, a hydrogen atom; a linear or branched C₁-C₃ alkyl radical optionally substituted by one or more radicals chosen from the hydroxyl, C₁-C₂ alkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals; a phenyl radical optionally substituted by one or more radicals chosen from amino, C₁-C₂ (di)alkylamino or (poly)hydroxyalkylamino radicals; R₁ and R₂ together form a 5- or 6-membered heterocycle optionally substituted by one or more radicals chosen from methyl, hydroxyl, amino or (di)methylamino radicals, a sulfonylamino radical, a C₂-C₄ (poly)hydroxyalkylamino radical, a carboxyl radical or a carboxamido radical.

According to a particularly preferred embodiment, R₁ and R₂ represent, preferably and independently of one another, a hydrogen atom; a linear or branched C₁-C₃ alkyl radical, such as methyl, ethyl, 2-hydroxyethyl, 2-aminoethyl; 1-carboxymethyl, 2-carboxyethyl, 2-sulfonylethyl, 2-methoxyethyl; a phenyl radical optionally substituted by one or more radicals chosen from amino, C₁-C₂ (di)alkylamino or (poly)hydroxyalkylamino radicals; R₁ and R₂ together form a 5- or 6-membered heterocycle pyrrolidine or piperidine optionally substituted by one or more methyl, hydroxyl, amino, (di)methylamino, carboxyl or carboxamido radicals.

R₁ and R₂ represent, preferably and independently of one another, a hydrogen atom; a methyl or 2-hydroxyethyl radical; a phenyl radical optionally substituted by an amino, (di)methylamino or (di)(2-hydroxyethyl)amino radical; R₁ and R₂ together form a 5- or 6-membered heterocycle such as pyrrolidine, 3-hydroxypyrrolidine, piperidine or 3-hydroxypiperidine.

R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃ represent, preferably and independently of one another, a hydrogen atom; a linear or branched C₁-C₄ alkyl radical optionally substituted by one or more radicals chosen from the hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals; a phenyl radical optionally substituted by one or more radicals chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals or a halogen atom such as chlorine, fluorine or bromine; a carboxyl radical; a sulfonylamino radical; a sulfonic radical; a C₁-C₂ alkoxy radical; a C₂-C₄ (poly)hydroxyalkoxy radical; an amino radical; a C₁-C₂ (di)alkylamino radical; a C₂-C₄ (poly)hydroxyalkylamino radical.

More preferably, R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃ represent a hydrogen atom, a C₁-C₄ alkyl radical optionally substituted by one or more radicals chosen from the hydroxyl, amino or C₁-C₂ (di)alkylamino radicals; a carboxyl radical; a C₁-C₂ alkoxy radical; an amino radical; a C₁-C₂ (di)alkylamino radical; a C₂-C₄ (poly)hydroxyalkylamino radical.

According to a particularly preferred embodiment, R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃ represent a hydrogen atom, a methyl, phenyl or 2-hydroxymethyl radical, a carboxyl, a methoxy, ethoxy or 2-hydroxyethyloxy radical, an amino, methylamino, dimethylamino or 2-hydroxyethylamino radical.

R₇ and R₉ represent, independently of one another, a hydrogen atom; a linear or branched C₁-C₄ alkyl radical, optionally substituted by one or more radicals chosen from the hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals; an optionally substituted phenyl radical; a carboxyl radical; a sulfonylamino radical.

Among these substituents, R₇ and R₉ preferably represent a hydrogen atom, a phenyl radical, a C₁-C₄ alkyl radical optionally substituted by one or more radicals chosen from the hydroxyl, amino, C₁-C₂ (di)alkylamino and carboxyl radicals.

According to a particularly preferred embodiment, R₇ and R₉ preferably represent a hydrogen atom, a methyl, phenyl or 2-hydroxymethyl radical, or a carboxyl.

R₈ preferably represents a C₁-C₄ alkyl radical optionally substituted by one or more radicals chosen from hydroxyl, C₁-C₂ alkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals. According to a particularly preferred embodiment, R₈ preferably represents a methyl, ethyl, 2-hydroxyethyl, 1-carboxymethyl, 2-carboxyethyl or 2-sulfonylethyl radical.

According to a particular embodiment, W1 and W6 are NR₁R₂ and R₁ and R₂ are preferably chosen from hydrogen, an alkyl radical which can be substituted by a hydroxyl or an amino.

According to another embodiment, W1 and W6 are OR and R is preferably a methyl radical.

In formula (I), W2 and W5 are preferably carbonaceous aromatic radicals. Preferably, W2 and W5 represent a phenyl radical optionally substituted by an alkyl, alkoxy, amino, or mono- or di-substituted amino radical. By way of example, W2 and W5 are phenyl radicals substituted by a methoxy radical, a methyl radical, an amino radical, a methylamino radical or a dimethylamino radical.

W3 and W4 are preferably chosen from imidazolinium, triazolium and pyridinium radicals.

According to a particularly preferred embodiment, W2 and W5 are phenylene radicals, W3 and W4 are imidazolinium radicals.

In formula (I), L is preferably a linear or branched C₁-C₈ alkylene radical, optionally substituted by one or more radicals chosen from the hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl or sulfonic radicals; preferably a linear or branched C₁-C₈ alkylene radical. According to a preferred embodiment, L is a linear or branched C₁-C₈ alkylene radical, optionally substituted by one or more radicals chosen from the hydroxyl, C₁-C₂ alkoxy, amino and C₁-C₂ (di)alkylamino radicals.

The concentration of dicationic diazo dye of formula (I) can vary between 0.001 and 5% by weight approximately relative to the total weight of the dyeing composition, and preferably between approximately 0.05 and 2%.

The composition of the invention can furthermore comprise an oxidizing agent. This oxidizing agent can be any oxidizing agent conventionally used for bleaching keratinous fibers. The oxidizing agent is preferably chosen from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulfates. The use of hydrogen peroxide is particularly preferred.

The composition according to the invention can furthermore comprise an oxidation base. This oxidation base can be chosen from the oxidation bases conventionally used in oxidation dyeing, for example para-phenylenediamines, bisphenylalkylenediamines, para-aminophenols, ortho-aminophenols and heterocyclic bases.

Mention may more particularly be made, among para-phenylenediamines, by way of example, of para-phenylenediamine, para-tolylenediamine, 2-chloro-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,5-dimethyl-para-phenylenediamine, N,N-dimethyl-para-phenylenediamine, N,N-diethyl-para-phenylenediamine, N,N-dipropyl-para-phenylenediamine, 4-amino-N,N-diethyl-3-methylaniline, N,N-bis(β-hydroxyethyl)-para-phenylenediamine, 4-N,N-bis(β-hydroxyethyl)amino-2-methylaniline, 4-N,N-bis(β-hydroxyethyl)amino-2-chloroaniline, 2-(β-hydroxyethyl)-para-phenylenediamine, 2-fluoro-para-phenylenediamine, 2-isopropyl-para-phenylenediamine, N-(β-hydroxypropyl)-para-phenylenediamine, 2-hydroxymethyl-para-phenylenediamine, N,N-dimethyl-3-methyl-para-phenylenediamine, N,N-(ethyl, β-hydroxyethyl)-para-phenylenediamine, N-(β,γ-dihydroxypropyl)-para-phenylenediamine, N-(4′-aminophenyl)-para-phenylenediamine, N-phenyl-para-phenylenediamine, 2-(β-hydroxyethyloxy)-para-phenylenediamine, 2-(β-acetylaminoethyloxy)-para-phenylenediamine, N-(β-methoxyethyl)-para-phenylenediamine, 4-(aminophenyl)pyrrolidine, 2-thienyl-para-phenylenediamine, 2-(β-hydroxyethylamino)-5-aminotoluene, and their addition salts with an acid.

Among the para-phenylenediamines mentioned above, para-phenylenediamine, para-tolylenediamine, 2-isopropyl-para-phenylenediamine, 2-(β-hydroxyethyl)-para-phenylenediamine, 2-(β-hydroxyethyloxy)-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, N,N-bis(β-hydroxyethyl)-para-phenylenediamine, 2-chloro-para-phenylenediamine, 2-(β-acetylaminoethyloxy)-para-phenylenediamine, and their addition salts with an acid, are particularly preferred.

Mention may be made, among bisphenylalkylene-diamines, by way of example, of N,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)-1,3-diaminopropanol, N,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)ethylenediamine, N,N′-bis(4-aminophenyl)tetramethylenediamine, N,N′-bis(β-hydroxyethyl)-N,N′-bis(4-aminophenyl)tetramethylenediamine, N,N′-bis(4-methylaminophenyl)tetramethylenediamine, N,N′-bis(ethyl)-N,N′-bis(4′-amino-3′-methylphenyl)-ethylenediamine, 1,8-bis(2,5-diaminophenoxy)-3,6-dioxaoctane, and their addition salts with an acid.

Mention may be made, among para-aminophenols, by way of example, of para-aminophenol, 4-amino-3-methylphenol, 4-amino-3-fluorophenol, 4-amino-3-(hydroxymethyl)phenol, 4-amino-2-methylphenol, 4-amino-2-(hydroxymethyl)phenol, 4-amino-2-(methoxymethyl)phenol, 4-amino-(2-aminomethyl)phenol, 4-amino-2-[(β-hydroxy-ethyl)aminomethyl]phenol, 4-amino-2-fluorophenol, and their addition salts with an acid.

Mention may be made, among ortho-aminophenols, by way of example, of 2-aminophenol, 2-amino-5-methylphenol, 2-amino-6-methylphenol, 5-acetamido-2-aminophenol, and their addition salts with an acid.

Mention may be made, among heterocyclic bases, by way of example, of pyridine derivatives, pyrimidine derivatives and pyrazole derivatives.

Mention may be made, among pyridine derivatives, of the compounds disclosed, for example, in Patents GB 1 026 978 and GB 1 153 196, such as 2,5-diaminopyridine, 2-(4-methoxyphenyl)amino-3-aminopyridine, 2,3-diamino-6-methoxypyridine, 2-(β-methoxyethyl)amino-3-amino-6-methoxypyridine, 3,4-diaminopyridine, and their addition salts with an acid.

Mention may be made, among pyrimidine derivatives, of the compounds disclosed, for example, in Patents DE 2 359 399, JP 88-169 571, JP 05 163 124 or EP 0 770 375 or Patent Application WO 96/15765, such as 2,4,5,6-tetraaminopyrimidine, 4-hydroxy-2,5,6-triaminopyrimidine, 2-hydroxy-4,5,6-triaminopyrimidine, 2,4-dihydroxy-5,6-diaminopyrimidine or 2,5,6-triaminopyrimidine, and pyrazolopyrimidine derivatives, such as those mentioned in Patent Application FR-A-2 750 048, among which may be mentioned pyrazolo[1,5-a]pyrimidine-3,7-diamine, 2,5-dimethylpyrazolo [1,5-a]pyrimidine-3,7-diamine, pyrazolo[1,5-a]pyrimidine-3,5-diamine, 2,7-dimethylpyrazolo[1,5-a]pyrimidine-3,5-diamine, 3-aminopyrazolo[1,5-a]pyrimidin-7-ol, 3-aminopyrazolo[1,5-a]pyrimidin-5-ol, 2-(3-aminopyrazolo[1,5-a]pyrimidin-7-ylamino)ethanol, 2-(7-aminopyrazolo[1,5-a]pyrimidin-3-ylamino)ethanol, 2-[(3-aminopyrazolo[1,5-a]pyrimidin-7-yl)(2-hydroxyethyl)amino]ethanol, 2-[(7-aminopyrazolo[1,5-a]pyrimidin-3-yl)(2-hydroxyethyl)amino]ethanol, 5,6-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine, 2,6-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine, 2,5,N7,N7-tetramethylpyrazolo[1,5-a]pyrimidine-3,7-diamine, 3-amino-5-methyl-7-(imidazolylpropylamino)pyrazolo[1,5-a]pyrimidine, and their addition salts with an acid and their tautomeric forms, when a tautomeric equilibrium exists.

Mention may be made, among pyrazole derivatives, of the compounds disclosed in Patents DE 3 843 892 and DE 4 133 957 and Patent Applications WO 94/08969, WO 94/08970, FR-A-2 733 749 and DE 195 43 988, such as 4,5-diamino-1-methylpyrazole, 4,5-diamino-1-(β-hydroxyethyl)pyrazole, 3,4-diaminopyrazole, 4,5-diamino-1-(4′-chlorobenzyl)pyrazole, 4,5-diamino-1,3-dimethylpyrazole, 4,5-diamino-3-methyl-1-phenylpyrazole, 4,5-diamino-1-methyl-3-phenylpyrazole, 4-amino-1,3-dimethyl-5-hydrazinopyrazole, 1-benzyl-4,5-diamino-3-methylpyrazole, 4,5-diamino-3-tert-butyl-1-methylpyrazole, 4,5-diamino-1-tert-butyl-3-methyl-pyrazole, 4,5-diamino-1-(β-hydroxyethyl)-3-methylpyrazole, 4,5-diamino-1-ethyl-3-methylpyrazole, 4,5-diamino-1-ethyl-3-(4′-methoxyphenyl)pyrazole, 4,5-diamino-1-ethyl-3-(hydroxymethyl)pyrazole, 4,5-diamino-3-hydroxymethyl-1-methylpyrazole, 4,5-diamino-3-hydroxymethyl-1-isopropylpyrazole, 4,5-diamino-3-methyl-1-isopropylpyrazole, 4-amino-5-(2′-aminoethyl)amino-1,3-dimethylpyrazole, 3,4,5-triaminopyrazole, 1-methyl-3,4,5-triaminopyrazole, 3,5-diamino-1-methyl-4-(methylamino)pyrazole, 3,5-diamino-4-(β-hydroxyethyl) amino-1-methylpyrazole, and their addition salts with an acid.

The composition according to the invention can additionally comprise one or more couplers conventionally used for the conventional oxidation dyeing of keratinous fibers. Mention may in particular be made, among these couplers, of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene couplers and heterocyclic couplers.

Mention may be made, by way of example, of 2-methyl-5-aminophenol, 5-N-(β-hydroxyethyl)amino-2-methylphenol, 6-chloro-2-methyl-5-aminophenol, 3-aminophenol, 1,3-dihydroxybenzene, 1,3-dihydroxy-2-methylbenzene, 4-chloro-1,3-dihydroxybenzene, 2,4-diamino-1-(β-hydroxyethyloxy)benzene, 2-amino-4-(β-hydroxyethylamino)-1-methoxybenzene, 1,3-diaminobenzene, 1,3-bis(2,4-diaminophenoxy)propane, 3-ureidoaniline, 3-ureido-1-dimethylaminobenzene, sesamol, 1-(β-hydroxyethylamino)-3,4-methylenedioxybenzene, α-naphthol, 2-methyl-1-naphthol, 6-hydroxyindole, 4-hydroxyindole, 4-hydroxy-N-methylindole, 2-amino-3-hydroxypyridine, 6-hydroxybenzomorpholine, 3,5-diamino-2,6-dimethoxypyridine, 1-N-(β-hydroxyethyl)amino-3,4-methylenedioxybenzene, 2,6-bis(β-hydroxyethylamino)toluene, and their addition salts with an acid.

In the composition of the present invention, the coupler or couplers are generally present in an amount of between 0.001 and 10% by weight approximately of the total weight of the dyeing composition and more preferably from 0.005 to 6%. The oxidation base or bases are present in an amount preferably of between 0.001 and 10% by weight approximately of the total weight of the dyeing composition and more preferably from 0.005 to 6%.

Generally, the addition salts with an acid which can be used in the context of the dyeing compositions of the invention for the oxidation bases and the couplers are chosen in particular from hydrochlorides, hydrobromides, sulfates, citrates, succinates, tartrates, lactates, tosylates, benzenesulfonates, phosphates and acetates.

The dyeing composition in accordance with the invention can additionally contain direct dyes different from those of formula (I), it being possible for these dyes in particular to be chosen from nitro dyes of the benzene series, cationic direct dyes, direct azo dyes and direct methine dyes.

The medium acceptable for dyeing, also referred to as dyeing support, is generally composed of water or of a mixture of water and of at least one organic solvent, in order to dissolve the compounds which would not be sufficiently soluble in water. Mention may be made, as organic solvent, for example, of lower C₁-C₄ alkanols, such as ethanol and isopropanol; polyols and polyol ethers, such as 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethylene glycol monomethyl ether; and aromatic alcohols, such as benzyl alcohol or phenoxyethanol; and their mixtures.

The solvents can be present in proportions preferably of between 1 and 40% by weight approximately with respect to the total weight of the dyeing composition and more preferably still between 5 and 30% by weight approximately.

The dyeing composition in accordance with the invention can also include various adjuvants conventionally used in hair dyeing compositions, such as anionic, cationic, nonionic, amphoteric or zwitterionic surface-active agents or their mixtures, anionic, cationic, nonionic, amphoteric or zwitterionic polymers or their mixtures, inorganic or organic thickening agents and in particular anionic, cationic, nonionic and amphoteric associative polymer thickeners, antioxidants, penetration agents, sequestering agents, fragrances, buffers, dispersing agents, conditioning agents, such as, for example, volatile or nonvolatile and modified or unmodified silicones, film-forming agents, ceramides, preservatives or opacifying agents.

These above adjuvants are generally present in an amount of, for each of them, between 0.01 and 20% by weight with respect to the weight of the composition.

Of course, a person skilled in the art will take care to choose this or these optional additional compounds so that the advantageous properties intrinsically attached to the dyeing composition in accordance with the invention are not, or not substantially, detrimentally affected by the envisaged addition or additions.

The pH of the dyeing composition in accordance with the invention is generally between 3 and 12 approximately and preferably between 5 and 11 approximately. It can be adjusted to the desired value by means of acidifying or basifying agents commonly used in dyeing keratinous fibers or alternatively using conventional buffer systems.

Mention may be made, among acidifying agents, by way of example, of inorganic or organic acids, such as hydrochloric acid, orthophosphoric acid, sulfuric acid, carboxylic acids, such as acetic acid, tartaric acid, citric acid or lactic acid, or sulfonic acids.

Mention may be made, among basifying agents, by way of example, of ammonia, alkaline carbonates, alkanolamines, such as mono-, di- and triethanolamines, and their derivatives, sodium hydroxide, potassium hydroxide and the compounds of following formula (III):

in which W is a propylene residue optionally substituted by a hydroxyl group or a C₁-C₄ alkyl radical and R_(a), R_(b), R_(c) and R_(d), which are identical or different, represent a hydrogen atom or a C₁-C₄ alkyl or C₁-C₄ hydroxyalkyl radical.

The dyeing composition according to the invention can be provided in various forms, such as in the form of liquids, creams or gels or in any other form appropriate for carrying out dyeing of keratinous fibers and in particular of human hair.

Another subject matter of the invention is a direct dyeing process which comprises the application of a dyeing composition comprising a dye of formula (I) as defined above to keratinous fibers. After a leave-in time, the keratinous fibers are rinsed, allowing colored fibers to appear.

The application to the fibers of the dyeing composition comprising the cationic azo dye of formula (I) can be carried out in the presence of an oxidizing agent which brings about the bleaching of the fiber. This oxidizing agent can be added to the composition comprising the cationic azo dye at the time of use or directly to the keratinous fiber. According to a specific embodiment, the composition comprising the cationic azo dye of formula (I) is free of oxidation base and of coupler.

Another subject matter of the invention is an oxidation dyeing process which comprises the application to fibers of a dyeing composition which comprises a dye of formula (I), at least one oxidation base and optionally at least one coupler, in the presence of an oxidizing agent.

The oxidation base, the coupler and the oxidizing agent are as defined above.

In the context of permanent oxidation dyeing, it is also possible to use, as oxidizing agent, enzymes among which may be mentioned peroxidases, 2-electron oxidoreductases, such as uricases, and 4-electron oxygenases, such as laccases.

The color can be developed at acidic, neutral or alkaline pH and the oxidizing agent can be added to the composition of the invention either at the time of use or it can be employed from an oxidizing composition comprising it, applied to the fibers simultaneously with or sequentially to the dyeing composition.

In the case of permanent oxidation dyeing or of direct dyeing, the dyeing composition is mixed, preferably at the time of use, with a composition comprising, in a medium acceptable for dyeing, at least one oxidizing agent, this oxidizing agent being present in an amount sufficient to develop a coloring. The mixture obtained is subsequently applied to the keratinous fibers. After a leave-in time of 3 to 50 minutes approximately, preferably 5 to 30 minutes approximately, the keratinous fibers are rinsed, washed with a shampoo, rinsed again and then dried.

The oxidizing composition can also include various adjuvants conventionally used in hair dyeing compositions and as defined above.

The pH of the oxidizing composition including the oxidizing agent is such that, after mixing with the dyeing composition, the pH of the resulting composition applied to keratinous fibers preferably varies between 3 and 12 approximately, and more preferably still between 5 and 11. It can be adjusted to the desired value by means of acidifying or basifying agents commonly used in dyeing keratinous fibers and as defined above.

The composition which is finally applied to the keratinous fibers can be provided in various forms, such as in the form of liquids, creams or gels or in any other form appropriate for carrying out dyeing of keratinous fibers and in particular of human hair.

Another subject matter of the invention is a multi-compartment device or dyeing ‘kit’ in which a first compartment includes the dyeing composition of the invention and a second compartment includes the oxidizing composition. This device can be equipped with a means allowing the desired mixture to be delivered to the hair, such as the devices disclosed in Patent FR 2 586 913 on behalf of the Applicant Company.

Finally, another subject matter of the invention is the dicationic diazo dyes of formula (I) as defined above. These compounds can be obtained from the preparation processes described for example in the documents EP 810824, GB 9619573, RO 106572, J. Chem. Res., Synop. (1998), (10), 648-649, DE 19721619, U.S. Pat. No. 5,852,179, Synth. Commun 1999, 29(13), 2271-2276.

The following examples serve to illustrate the invention without, however, exhibiting a limiting nature.

EXAMPLES Examples of Synthesis Example No. 1

Preparation of a Compound of Formula:

1.13 g of dimethyl-[4-(pyridin-3-ylazo)phenyl1]amine (0.01 mol), 5 ml of dry DMF and 0.61 g (0.0025 mol) of 1,6-dibromohexane are charged to a fully equipped round-bottomed flask. The mixture is brought for 7 hours to 105° C. with stirring. The precipitate is filtered off in the hot state. 0.9 g of a Bordeaux red powder having the following

UV absorption characteristics is obtained: UV (acetonitrile-water 50/50) λ_(max) = 496 nm ε_(max) = 67600 Analyses: Mass ESI+: m/z = 617 [M²⁺ + Br⁻] m/z = 268 [M²⁺/2]

¹H NMR: (400 MHZ-DMSO) ppm: 1.40 (s-4H); 2.01 (s-4H) CH₂ hexyl 3.15 (s-12H)-NCH₃; 4.73 (t-4H)-NCH₂; 6.91 (d-4H); 7.88 (d-4H) phenyl 8.33 (dd-2H); 8.76 (d-2H); 9.11 (d-2H); 9.54 (s-2H) pyridine

A dye giving an intense orange-red color is thus obtained.

The dimethyl-[4-(pyridin-3-ylazo)phenyl1]amine can be prepared by coupling the diazonium salt of 3-amino-pyridine with dimethylaniline according to the conventional methods for preparing azo compounds or according to the teaching of patent DE2509560.

Example No. 2

Preparation of a Compound of Formula:

1st step: 1,6-bis[N-imidazol-2-yl)-4(4-methoxyphenyl)-diazene]:

2.02 g (0.01 mol) of (1H-imidazol-2-yl)-(4-methoxy-phenyl)diazene, 50 ml of toluene and 1.21 g (0.005 mol) of 1,6-dibromohexane, 1.92 g (0.048 mol) of sodium hydroxide, (0.0003 mol) of tetrabutylammonium iodide and 2 ml of water are charged to a fully equipped round-bottomed flask. The mixture is brought for 20 hours to the reflux temperature, with stirring. The precipitate is cooled, filtered off and dried. 0.9 g of an orange-yellow powder is obtained which is purified by chromatography on silica (eluent: dichloromethane 95/methanol 5).

Analyses: Mass ESI+: m/z = 487 [M⁺⁻]

¹H NMR: (400 MHz-DMSO) ppm: 1.27 (s-4H); 1.74 (s-4H) CH₂ hexyl 3.85 (s-6H)-OCH₃; 4.33 (t-4H)-NCH₂; 7.16 (d-4H); 7.82 (d-4H) phenyl 7.51 (s-2H) imidazole

The preparation of this type of diamines is described in patent application WO 99/37276 and also in the following documents: J. Elguero et al., Journal of Heterocyclic Chemistry 2-5, 771-782 (1988), Ying-hung So, Macromolecules 25, 516-520 (1992) and R. G. Xie et al., Chinese Chemical Letters 7, 321-324 (1996).

2nd step: Quaternization:

0.6 g (0.0012 mol) of the product obtained above, 4 ml of dichloroethane and 0.47 ml (0.0048 mol) of dimethyl sulfate are charged to a fully equipped round-bottomed flask. The mixture is brought for 2 hours to the ref lux temperature, with stirring. The precipitate is cooled, filtered off and dried. 0.6 g of an orange-yellow powder having the following UV absorption characteristics is obtained:

UV (ethanol) λ_(max) = 406 nm shoulder at 450 nm ε_(max) = 53400

¹H NMR: (400 MHz-DMSO) ppm: 1.37 (s-4H); 1.79 (s-4H) CH₂ hexyl 3.94 (s-6H)-OCH₃; 4.45 (t-4H)-NCH₂; 4.04 (s-6H-NCH3 7.24 (d-4H); 7.07 (d-4H) phenyl 7.96 (d-4H) imidazole

A dye giving an intense yellow color is thus obtained.

Example No. 3

Preparation of a Compound of Formula:

0.3 g of the product obtained above (0.0004 mol), 2 ml of dry DMF and 0.57 g (0.008 mol) of pyrrolidine are charged to a fully equipped round-bottomed flask. The mixture is brought for 1.5 hours to 100° C., with stirring. The reaction mixture is poured into 50 ml of ethyl acetate. The precipitate is drained and dried. 0.4 g of a Bordeaux red powder having the following UV absorption characteristics is obtained:

UV (ethanol) λ_(max) = 534 nm ε_(max) = 86000

¹H NMR: (400 MHz-DMSO) ppm: 1.35 (s-4H); 1.77 (s-4H) CH₂ hexyl 2.02 (m-8H); 3.44 (unreserved complex HDO+8H) pyrrolidine 4.32 (t-4H)-NCH₂; 3.92 (s-6H)-NCH3 6.77 (d-4H); 7.84 (d-4H) phenyl 7.69 (d-2H); 7.72 (d-4H) imidazole

A dye having an intense red color is thus obtained.

Dyeing Examples

The following dyeing compositions were prepared:

Example 4 5 Azo dye of example 1 5 × 10⁻⁴ mol — Dye of example 3 — 5 × 10⁻⁴ mol Polyethylene glycol 8 EO  12 g  12 g Benzyl alcohol  10 g  10 g Borate buffer q.s. 100 g 100 g pH 8.9 9.1

At the time of use, each composition is mixed with an equal weight of 20-volumes hydrogen peroxide (6% by weight).

Each mixture obtained is applied to locks of gray hair comprising 90% permanently waved (BP) or natural (BN) white hair (1 g of lock per 10 g of solution). After allowing the mixture to act for 20 min, the locks are rinsed, washed with a standard shampoo, rinsed again and then dried.

Each lock is evaluated before and after dyeing in the L*a*b* system, by means of a CM 2002 MINOLTA® spectrophotometer (illuminant D65).

In the L*a*b* space, the lightness is indicated by the value L* on a scale from 0 to 100 whereas the chromatic coordinates are expressed by a* and b* which indicate two color axes, a* the red-green axis and b* the yellow-blue axis.

According to this system, the higher the value of L, the lighter and less intense the color. Conversely, the lower the value of L, the darker or more intense the color.

The following dyeing results were obtained.

Natural hair Permanently waved hair L* a* b* L* a* b* Example 4 23.6 15.8 11.2 22.5 15.7 10.1 Example 5 21.8 16.7 7.0 20.1 13.9 4.5 

1. A composition for dyeing keratinous fibers comprising at least one dicationic diazo dye chosen from those of the following formula (I): W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆ wherein: W₁ and W₆, which may be identical or different, are each chosen from radicals NR₁R₂ and OR; W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic, pyridine and pyridazinyl groups of formula (II)

W₃ and W₄, which may be identical or different, are each chosen from heteroaromatic radicals of the following formulae (III) and (IV):

wherein: X₁ is chosen from a nitrogen atom and radicals CR₅; X₂ is chosen from a nitrogen atom and radicals CR₆; Z₁ is chosen from an oxygen atom, a sulfur atom, and radicals NR₈; Z₂ is chosen from a nitrogen atom and radicals CR₉; Z₃ is chosen from a nitrogen atom and radicals CR₁₂; Z₄ is chosen from a nitrogen atom and radicals CR₁₃; N¹ of the 5-membered ring of formula (III) is connected to the group L and the bond a of the same 5-membered ring is connected to the azo group of formula (I); the bond b of the 6-membered ring of formula (IV) is connected to the azo group of formula (I) and N¹ of the 6-membered ring of formula (IV) is connected to the group L; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from linear and branched C₁-C₁₆ hydrocarbonaceous chains, which can form at least one ring chosen from 3- to 6-membered carbonaceous rings, and which can be saturated or unsaturated, wherein at least one carbon atom of the hydrocarbonaceous chains can be replaced by at least one entity chosen from oxygen, nitrogen, and sulfur atoms and an SO₂ group, and the at least one carbon atom of the hydrocarbonaceous chains can be substituted by at least one atom chosen from halogen atoms; R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can each independently be a hydrogen atom; provided that L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ do not comprise a peroxide bond, a diazo radical, or a nitroso radical, and L is a divalent radical; R₈ is chosen from linear and branched C₁-C₈ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; and from optionally substituted phenyl radicals; R₇ with R₉, R₁₀ with R₁₁ and R₁₂ with R₁₃ can form a carbonaceous aromatic ring; R is a radical chosen from C₁-C₃ alkyl radicals; and X⁻ is an anion chosen from organic and inorganic anions.
 2. The composition according to claim 1, wherein the keratinous fibers are human keratinous fibers.
 3. The composition according to claim 2, wherein the human keratinous fibers are hair.
 4. The composition according to claim 1, wherein: R₁ and R₂, which may be identical or different, are each chosen from a hydrogen atom; linear and branched C₁-C₆ alkyl radicals, optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; phenyl radicals optionally substituted by at least one entity chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals and from halogen atoms; C₁-C₄ alkylsulfonyl radicals; arylsulfonyl radicals; and pyrazolyl, imidazolyl, thiazolyl, oxazolyl, thiadiazolyl, triazolyl, pyrrolyl, pyridyl, pyrimidinyl, triazinyl, pyrazinyl and pyridazinyl radicals; R₁ and R₂ may together form a heterocycle chosen from 5-, 6-, 7- and 8-membered heterocycles optionally substituted by at least one radical chosen from a hydroxyl radical; an amino radical; a radical —NR₁₄R₁₅, wherein R₁₄ and R₁₅, which may be identical or different, are each chosen from a hydrogen atom, linear and branched C₁-C₄ alkyl radicals substituted by at least one entity chosen from a halogen atom, and from hydroxyl, C₁-C₂ alkoxy, amino, C₁-C₂ amino(di)alkyl, and (poly)hydroxyalkylamino radicals; a sulfonylamino radical; a carboxyl radical; a carboxamido radical; and C₁-C₆ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl and amino radicals and from a radical —NR₁₄R₁₅; or R₁ and R₂ together form a heteroaromatic radical chosen from 5- and 6-membered heteroaromatic radicals.
 5. The composition according to claim 4, wherein R₁ and R₂, which may be identical or different, are each chosen from a hydrogen atom; linear and branched C₁-C₃ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; phenyl radicals optionally substituted by at least one radical chosen from amino, C₁-C₂ (di)alkylamino and (poly)hydroxyalkylamino radicals or R₁ and R₂ together form a heterocycle chosen from 5- and 6-membered heterocycles optionally substituted by at least one radical chosen from methyl, hydroxyl, amino, (di)methylamino, sulfonylamino, C₂-C₄ (poly)hydroxyalkylamino, carboxyl and carboxamido radicals.
 6. The composition according to claim 5, wherein, R₁ and R₂, which may be identical or different, are each chosen from a hydrogen atom; from methyl, ethyl, 2-hydroxyethyl, 2-aminoethyl, 1-carboxymethyl, 2-carboxyethyl, 2-sulfonylethyl, and 2-methoxyethyl radicals; from phenyl radicals optionally substituted by at least one radical chosen from amino, C₁-C₂ (di)alkylamino and (poly)hydroxyalkylamino radicals or R₁ and R₂ together form a 5- or 6-membered heterocycle chosen from pyrrolidine and piperidine optionally substituted by at least one radical chosen from methyl, hydroxyl, amino, (di)methylamino, carboxyl and carboxamido radicals.
 7. The composition according to claim 6, wherein, R₁ and R₂, which may be identical or different, are each chosen from a hydrogen atom; methyl and 2-hydroxyethyl radicals; phenyl radicals optionally substituted by at least one radical chosen from amino, (di)methylamino and (di)(2-hydroxyethyl)amino radicals; R₁ and R₂ together form a 5- or 6-membered heterocycle chosen from pyrrolidine, 3-hydroxypyrrolidine, piperidine and 3-hydroxypiperidine; or R₁ and R₂ together form a 5- or 6-membered heteroaromatic radical chosen from pyrazole, imidazole, pyrrole, triazole, pyridazine and pyrimidine.
 8. The composition according to claim 1, wherein R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from a hydrogen atom; linear and branched C₁-C₄ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; phenyl radicals optionally substituted by at least one entity chosen from halogen atoms and from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl, and sulfonic radicals; a carboxyl radical; a sulfonylamino radical; a sulfonic radical; C₁-C₂ alkoxy radicals; C₂-C₄ (poly)hydroxyalkoxy radicals; an amino radical; C₁-C₂ (di)alkylamino radicals; and C₂-C₄ (poly)hydroxyalkylamino radicals.
 9. The composition according to claim 8, wherein the halogen atoms are chosen from chlorine, fluorine, and bromine.
 10. The composition according to claim 8, wherein R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from a hydrogen atom, C₁-C₄ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, amino and C₁-C₂ (di)alkylamino radicals; a carboxyl radical; C₁-C₂ alkoxy radicals; an amino radical; C₁-C₂ (di)alkylamino radicals; and C₂-C₄ (poly)hydroxyalkylamino radicals.
 11. The composition according to claim 8, wherein R₃, R₄, R₅, R₆, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from a hydrogen atom, methyl, phenyl and 2-hydroxymethyl radicals, carboxyl, methoxy, ethoxy and 2-hydroxyethyloxy radicals, and amino, methylamino, dimethylamino and 2-hydroxyethylamino radicals.
 12. The composition according to claim 1, wherein R₇ and R₉, which may be identical or different, are each chosen from a hydrogen atom; linear and branched C₁-C₄ alkyl radicals, optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; an optionally substituted phenyl radical; a carboxyl radical; and a sulfonylamino radical.
 13. The composition according to claim 12, wherein R₇ and R₉, which may be identical or different, are each chosen from a hydrogen atom, a phenyl radical, C₁-C₄ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, amino, C₁-C₂ (di)alkylamino and carboxyl radicals.
 14. The composition according to claim 13, wherein R₇ and R₉, which may be identical or different, are each chosen from a hydrogen atom, methyl, phenyl, 2-hydroxymethyl and carboxyl radicals.
 15. The composition according to claim 1, wherein R₈ is chosen from C₁-C₄ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals.
 16. The composition according to claim 15, wherein R₈ is chosen from methyl, ethyl, 2-hydroxyethyl, 1-carboxymethyl, 2-carboxyethyl and 2-sulfonylethyl radicals.
 17. The composition according to claim 1, wherein L is chosen from linear and branched C₁-C₈ alkylene radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals.
 18. The composition according to claim 17, wherein L is chosen from linear and branched C₁-C₈ alkylene radicals.
 19. The composition according to claim 1, wherein W₁ and W₆, which may be identical or different, are each chosen from radical NR₁R₂, wherein R₁ and R₂, which may be identical or different, are each chosen from hydrogen, and alkyl radicals optionally substituted by at least one substituent chosen from hydroxyl and amino radicals.
 20. The composition according to claim 1, wherein W₁ and W₆, which may be identical or different, are each chosen from radical OR, wherein R is a methyl radical.
 21. The composition according to claim 1, wherein W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic radicals.
 22. The composition according to claim 4, wherein W₂ and W₅, which may be identical or different, are each chosen from phenyl radicals optionally substituted with at least one radical chosen from alkyl, alkoxy, amino, mono- and disubstituted amino radicals.
 23. The composition according to claim 22, wherein the phenyl radicals are optionally substituted with at least one radical chosen from methoxy, methyl, methylamino, and dimethylamino radicals.
 24. The composition according to claim 1, wherein W₃ and W₄, which may be identical or different, are each chosen from imidazolinium, triazolium, and pyridinium radicals.
 25. The composition according to claim 1, wherein the at least one dicationic diazo dye of formula (I) is chosen such that W₂ and W₅ are phenylene radicals and W₃ and W₄ are imidazolinium radicals.
 26. The composition according to claim 1, wherein L is chosen from linear and branched C₁-C₈ alkylene radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, amino and C₁-C₂ (di)alkylamino radicals.
 27. The composition according to claim 1, wherein the at least one dicationic diazo dye of formula (I) is chosen from compounds of the following formulae:


28. The composition according to claim 1, wherein the at least one dicationic diazo dye of formula (I) is a compound of the following formula:


29. The composition according to claim 1, further comprising at least one oxidation base.
 30. The composition according to claim 29, wherein the at least one oxidation base is chosen from para-phenylenediamines, bisphenylalkylenediamines, para-aminophenols, ortho-aminophenols, heterocyclic bases and the acid addition salts thereof.
 31. The composition according to claim 29, wherein the at least one oxidation base is present in an amount ranging from 0.001 to 10% by weight, relative to the total weight of the composition.
 32. The composition according to claim 31, wherein the at least one oxidation base is present in an amount ranging from 0.005 to 6% by weight, relative to the total weight of the composition.
 33. The composition according to claim 1, further comprising at least one coupler.
 34. The composition according to claim 33, wherein the at least one coupler is chosen from meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene couplers, heterocyclic couplers and the acid addition salts thereof.
 35. The composition according to claim 1, further comprising at least one oxidizing agent.
 36. The composition according to claim 35, wherein the at least one oxidizing agent is hydrogen peroxide.
 37. A process for the oxidation dyeing of keratinous fibers comprising applying, to the fibers, at least one dyeing composition comprising at least one dicationic diazo dye chosen from those of the following formula (I): W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆ wherein: W₁ and W₆, which may be identical or different, are each chosen from radicals NR₁R₂ and OR; W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic, pyridine and pyridazinyl groups of formula (II)

W₃ and W₄, which may be identical or different, are each chosen from heteroaromatic radicals of the following formulae (III) and (IV):

wherein: X₁ is chosen from a nitrogen atom and radicals CR₅; X₂ is chosen from a nitrogen atom and radicals CR₆; Z₁ is chosen from an oxygen atom, a sulfur atom, and radicals NR₈; Z₂ is chosen from a nitrogen atom and radicals CR₉; Z₃ is chosen from a nitrogen atom and radicals CR₁₂; Z₄ is chosen from a nitrogen atom and radicals CR₁₃; N¹ of the 5-membered ring of formula (III) is connected to the group L and the bond a of the same 5-membered ring is connected to the azo group of formula (I); the bond b of the 6-membered ring of formula (IV) is connected to the azo group of formula (I) and N¹ of the 6-membered ring of formula (IV) is connected to the group L; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from linear and branched C₁-C₁₆ hydrocarbonaceous chains, which can form at least one ring chosen from 3- to 6-membered carbonaceous rings, and which can be saturated or unsaturated, wherein at least one carbon atom of the hydrocarbonaceous chains can be replaced by at least one entity chosen from oxygen, nitrogen, and sulfur atoms and an SO₂ group, and the at least one carbon atom of the hydrocarbonaceous chains can be substituted by at least one atom chosen from halogen atoms; R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can each independently be a hydrogen atom; provided that L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ do not comprise a peroxide bond, a diazo radical, or a nitroso radical, and L is a divalent radical; R₈ is chosen from linear and branched C₁-C₈ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; and from optionally substituted phenyl radicals; R₇ with R₉, R₁₀ with R₁₁ and R₁₂ with R₁₃ can form a carbonaceous aromatic ring; R is a radical chosen from C₁-C₃ alkyl radicals; and X⁻ is an anion chosen from organic and inorganic anions.
 38. The process according to claim 37, wherein the keratinous fibers are human keratinous fibers.
 39. The process according to claim 38, wherein the human keratinous fibers are hair.
 40. The process according to claim 37, wherein the at least one dyeing composition further comprises at least one oxidizing agent.
 41. The process according to claim 40, wherein the at least one oxidizing agent is mixed at the time of application with the at least one dyeing composition.
 42. The process according to claim 40, wherein the at least one oxidizing agent is applied to the fibers in the form of at least one oxidizing composition simultaneously with or sequentially to the at least one dyeing composition.
 43. A process for the oxidation dyeing of keratinous fibers comprising applying to the fibers, in the presence of at least one oxidizing agent, at least one dyeing composition comprising, (A) at least one dicationic diazo dye chosen from those of the following formula (I): W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆ wherein: W₁ and W₆, which may be identical or different, are each chosen from radicals NR₁R₂ and OR; W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic, pyridine and pyridazinyl groups of formula (II)

W₃ and W₄, which may be identical or different, are each chosen from heteroaromatic radicals of the following formulae (III) and (IV):

wherein: X₁ is chosen from a nitrogen atom and radicals CR₅; X₂ is chosen from a nitrogen atom and radicals CR₆; Z₁ is chosen from an oxygen, a sulfur atom, and radicals NR₈; Z₂ is chosen from a nitrogen atom and radicals CR₉; Z₃ is chosen from a nitrogen atom and radicals CR₁₂; Z₄ is chosen from a nitrogen atom and radicals CR₁₃; N¹ of the 5-membered ring of formula (III) is connected to the group L and the bond a of the same 5-membered ring is connected to the azo group of formula (I); the bond b of the 6-membered ring of formula (IV) is connected to the azo group of formula (I) and N¹ of the 6-membered ring of formula (IV) is connected to the group L; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from linear and branched C₁-C₁₆ hydrocarbonaceous chains, which can form at least one ring chosen from 3- to 6-membered carbonaceous rings, and which can be saturated or unsaturated, wherein at least one carbon atom of the hydrocarbonaceous chains can be replaced by at least one entity chosen from oxygen, nitrogen, and sulfur atoms and an SO₂ group, and the at least one carbon atom of the hydrocarbonaceous chains can be substituted by at least one atom chosen from halogen atoms; R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can each independently be a hydrogen atom; provided that L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ do not comprise a peroxide bond, a diazo radical, or a nitroso radical, and L is a divalent radical; R₈ is chosen from linear and branched C₁-C₈ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; and from optionally substituted phenyl radicals; R₇ with R₉, R₁₀ with R₁₁ and R₁₂ with R₁₃ can form a carbonaceous aromatic ring; R is a radical chosen from C₁-C₃ alkyl radicals; and X⁻ is an anion chosen from organic and inorganic anions; (B) at least one oxidation base; and (C) optionally at least one coupler.
 44. The composition according to claim 43, wherein the keratinous fibers are human keratinous fibers.
 45. The composition according to claim 44, wherein the human keratinous fibers are hair.
 46. The process according to claim 43, wherein the at least one oxidizing agent is mixed at the time of application with the at least one dyeing composition.
 47. The process according to claim 43, wherein the at least one oxidizing agent is applied to the fibers in the form of at least one dyeing composition simultaneously with or sequentially to the at least one dyeing composition.
 48. A multi-compartment dyeing kit, comprising, (A) at least one first compartment comprising at least one dyeing composition comprising at least one dicationic diazo dye chosen from those of the following formula (I): W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆ wherein: W₁ and W₆, which may be identical or different, are each chosen from radicals NR₁R₂ and OR; W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic, pyridine and pyridazinyl groups of formula (II)

W₃ and W₄, which may be identical or different, are each chosen from heteroaromatic radicals of the following formulae (III) and (IV):

wherein: X₁ is chosen from a nitrogen atom and radicals CR₅; X₂ is chosen from a nitrogen atom and radicals CR₆; Z₁ is chosen from an oxygen atom, a sulfur atom, and radicals NR₈; Z₂ is chosen from a nitrogen atom and radicals CR₉; Z₃ is chosen from a nitrogen atom and radicals CR₁₂; Z₄ is chosen from a nitrogen atom and radicals CR₁₃; N¹ of the 5-membered ring of formula (III) is connected to the group L and the bond a of the same 5-membered ring is connected to the azo group of formula (I); the bond b of the 6-membered ring of formula (IV) is connected to the azo group of formula (I) and N¹ of the 6-membered ring of formula (IV) is connected to the group L; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from linear and branched C₁-C₁₆ hydrocarbonaceous chains, which can form at least one ring chosen from 3- to 6-membered carbonaceous rings, and which can be saturated or unsaturated, wherein at least one carbon atom of the hydrocarbonaceous chains can be replaced by at least one entity chosen from oxygen, nitrogen, and sulfur atoms and an SO₂ group, and the at least one carbon atom of the hydrocarbonaceous chains can be substituted by at least one atom chosen from halogen atoms R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can each independently be a hydrogen atom; provided that L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ do not comprise a peroxide bond, a diazo radical, or a nitroso radical, and L is a divalent radical; R₈ is chosen from linear and branched C₁-C₈ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; and from optionally substituted phenyl radicals; R₇ with R₉, R₁₀ with R₁₁, and R₁₂ with R₁₃ can form a carbonaceous aromatic ring; R is a radical chosen from C₁-C₃ alkyl radicals; and X⁻ is an anion chosen from organic and inorganic anions and (B) at least one second compartment comprising at least one oxidizing composition.
 49. A dicationic diazo compound chosen from those of the following formula (I) W₁—W₂—N═N—W₃—L—W₄—N═N—W₅—W₆ wherein: W₁ and W₆, which may be identical or different, are each chosen from radicals NR₁R₂and OR; W₂ and W₅, which may be identical or different, are each chosen from carbonaceous aromatic, pyridine and pyridazinyl groups of formula (II)

W₃ and W₄, which may be identical or different, are each chosen from heteroaromatic radicals of the following formulae (III) and (IV):

wherein: X₁ is chosen from a nitrogen atom and radicals CR₅; X₂ is chosen from a nitrogen atom and radicals CR₆; Z₁ is chosen from an oxygen atom, a sulfur atom, and radicals NR₈; Z₂ is chosen from a nitrogen atom and radicals CR₉; Z₃ is chosen from a nitrogen atom and radicals CR₁₂; Z₄ is chosen from a nitrogen atom and radicals CR₁₃; N¹ of the 5-membered ring of formula (III) is connected to the group L and the bond a of the same 5-membered ring is connected to the azo group of formula (I); the bond b of the 6-membered ring of formula (IV) is connected to the azo group of formula (I) and N¹ of the 6-membered ring of formula (IV) is connected to the group L; L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃, which may be identical or different, are each chosen from linear and branched C₁-C₁₆ hydrocarbonaceous chains, which can form at least one ring chosen from 3- to 6-membered carbonaceous rings, and which can be saturated or unsaturated, wherein at least one carbon atom of the hydrocarbonaceous chains can be replaced by at least one entity chosen from oxygen, nitrogen, and sulfur atoms and an SO₂ group, and the at least one carbon atom of the hydrocarbonaceous chains can be substituted by at least one atom chosen from halogen atoms; R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ can each independently be a hydrogen atom; provided that L, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ do not comprise a peroxide bond, a diazo radical, or a nitroso radical, and L is a divalent radical; R₈ is chosen from linear and branched C₁-C₈ alkyl radicals optionally substituted by at least one radical chosen from hydroxyl, C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, amino, C₁-C₂ (di)alkylamino, carboxyl and sulfonic radicals; and from optionally substituted phenyl radicals; R₇ with R₉, R₁₀ with R₁₁ and R₁₂ with R₁₃ can form a carbonaceous aromatic ring; R is a radical chosen from C₁-C₃ alkyl radicals; and X⁻ is an anion chosen from organic and inorganic anions, with the proviso that when Z₁ is a sulfur atom, then Z₂ is a nitrogen atom. 